Modern vehicles having internal combustion engines (ICE) create electrical power using an ancillary power unit (APU) that supplies electrical power for electrical devices on the vehicle and also recharges the vehicle battery. Typically, the APU is an alternator that converts mechanical energy from the ICE into electrical energy, which is stored in the battery. Several factors have lead to a search for new types of APUs.
Alternators are inefficient because fuel energy is first converted into mechanical energy, after which mechanical energy is converted into electrical energy. This process combines two inefficient power conversions. Alternator APUs generate electrical energy only when the ICE is operating. When the vehicle is stopped but the ICE is operating, the ICE can be run to power the APU, thereby consuming fuel. Alternatively, when the ICE is not operating, stored electric power can be used to power the electrical components of the vehicle although electrical power storage is heavy, costly and takes up space.
Developments in vehicle technology have lead to new types of power-consuming electrical systems such as hybrid drive-trains, advanced starting systems, air-conditioning, x-by-wire, computer processors, entertainment and telematics systems, for example. At the same time, there is increasing concern for fuel efficiency in vehicles. Thus, an APU that uses less vehicular fuel or an alternative fuel to produce electricity is a need in the industry.